Access control systems with a plurality of access control devices which control the access to access-controlled objects, for example access-controlled areas such as buildings, rooms or grounds, are known and are used, for instance, in hotels, company buildings and government buildings. In these known access control systems code carriers are handed out to the users, for example hotel guests or employees, in which code carriers a secret access code or an identification code is stored. The code carriers are designed, for example, as punch cards, magnetic cards, induction cards or chipcards, which transmit the access code stored thereon, or respectively the identification code, via an interface with contacts (mechanical or electrical) or via a contactless interface (by radio or infrared waves) to the access control device to be passed. In the access control device to be passed the received access code is compared with a secret access code stored in the access control device, or respectively the received identification code is transmitted by the access control device to an access control central unit for access authorization checking. In order to be able to change the secret access codes in the access control devices in a flexible and dynamic way, or respectively check the access authorization for an identification code in a centralized way, and in order to check further access conditions, such as authorized access time, authorized access day and/or authorized access date for the user, the access control devices in the known access control systems are connected to an access control central unit via fixed communication links. A drawback of these known access control systems is that a code carrier always has to be handed over or sent to the users personally, the sending entailing a security risk and therefore not being practiced, as a rule. During a change of code, the user must be given a new code carrier or an already handed out code carrier must be presented by the user at a service point for the code change. Moreover there is the disadvantage in the known access control systems that the administration of the access rights of the users or the sending of the access code to the users is always connected with an access control central unit. In the known access control systems therefore it is not possible to carry out the administration of the access rights of users to particular access-controlled objects in a plurality of access control central units independent of one another and/or to control the sending of the access code for these particular access-controlled objects to the users from a plurality of access control central units independent of one another.
Described in the patent application WO 01/63425 is an access control system for a hotel in which a secret code for a reserved hotel room is transmitted via a mobile radio network to a user to his mobile radio telephone and is stored there. According to WO 01/63425 the secret access code is transmitted from an access control central unit for the reserved point in time to the access control device of the reserved hotel room. To open the room door, the access code stored in the mobile radio telephone is transmitted via a wireless device interface to the access control device of the reserved hotel room. In the access control device, the received access code is compared with the access code stored there and, in the case of agreement, the electromechanical door lock of the room door is opened. In the access control system according to WO 01/63425, the access control device is networked with the access control central unit, which, on the one hand, entails a big investment in cabling, which increases the installation time and installation cost of the access control system and which, on the other hand, requires a corresponding communication module in each access control device, which increases the system costs.
Described in the patent application WO 01/40605 are an access control system and an access control method in which access rights for users and assigned access codes are administered and stored in an access control central unit. The access codes as well as indications such as security levels and access times are transmitted from the access control central unit over a telecommunication network to the respective access control devices. The access codes for the various access control devices are transmitted moreover from the access control central unit to the respective key devices, which can be designed as mobile communication terminals, for example mobile radio telephone. To pass an access control device, an access code stored in the key device is transmitted from there to the respective access control device, for example wirelessly. According to WO 01/63425, the access control devices must be designed for data communication with the access control central unit, which increases the system costs correspondingly. Moreover the user has to select the access code for the respective access control device from among several access codes stored in the key device, which entails a corresponding investment in time and which can be considered tedious by the user.
Described in the patent publication U.S. Pat. No. 5,565,857 is an access control system in which a plurality of user-specific access codes as well as an identification code in each case for the respective access control device are stored in the access control devices. According to U.S. Pat. No. 5,565,857, stored in the portable electronic key devices, which can be designed as mobile communication terminals, for example mobile radio telephones, are identification codes of a plurality of access control devices and assigned user-specific access codes. If a user with a key device is detected by the access control device, the identification code of the respective access control device is transmitted wirelessly to the key device. In the key device, the user-specific access code is determined which is stored, assigned to the received identification code of the access control device. The determined user-specific access code is transmitted from the key device wirelessly to the access control device, and is compared there with the stored user-specific access codes. In the access control system according to U.S. Pat. No. 5,565,857, the user-specific access codes are entered by an authorized user directly on location into the access control device, which is unsuitable for applications with several access control devices. In order to adapt the access control system according to U.S. Pat. No. 5,565,857 for applications with several access control devices, the access control devices would have to be networked with an access control central unit, which, on the one hand, entails a big investment in cabling, which increases the installation time and installation costs of the access control system, and, on the other hand, requires a corresponding communication module in each access control device, which increases the system costs.